Pediatric Oral Tablet Dosing: Weight-Based Recommendations
For children, all oral tablet dosing should be calculated using weight-based formulas (mg/kg/day) rather than age-based approximations, with children weighing more than 40 kg dosed as adults. 1, 2
General Dosing Principles
Weight-Based vs. Age-Based Dosing
- Weight-based dosing is the standard of care for pediatric medications because age-based dosing leads to significant underdosing or overdosing errors in up to 30% of children 3, 4
- Children weighing >40 kg should receive adult dosing for most medications 5, 2
- Body surface area (BSA) calculations are recommended for certain medications but are less practical for routine use 6
Practical Weight-Based Formula for General Use
- For children up to 30 kg: dose = (weight × 2)% of adult dose 6
- For children over 30 kg: dose = (weight + 30)% of adult dose 6
- This approach follows BSA curves more accurately than simple mg/kg calculations and reduces major prescribing errors 6
Common Oral Tablet Medications
Acetaminophen (Paracetamol)
- Standard dosing: 60 mg/kg/day divided into 4 doses (15 mg/kg every 6 hours) for pain or fever 3
- Available as tablets (various strengths), chewable tablets, and liquid suspensions 1
- Critical pitfall: The commonly recommended 10 mg/kg dose does NOT achieve therapeutic plasma concentrations (10-20 μg/mL) in most children 4
- 15 mg/kg dosing is necessary to reach adequate antipyretic levels 4
- Children >40 kg should receive adult dosing 1
Amoxicillin
- For uncomplicated infections: 60 mg/kg/day divided into 2 doses (30 mg/kg every 12 hours) 3
- For severe infections or lower respiratory tract infections:
- For mild/moderate ear, nose, throat, skin, or genitourinary infections:
- Infants <12 weeks: maximum 30 mg/kg/day divided every 12 hours due to immature renal function 2
Tuberculosis Medications (First-Line Agents)
Isoniazid:
Rifampin:
Pyrazinamide:
Ethambutol:
Influenza Antivirals
Oseltamivir (oral capsules/suspension):
- Treatment (5 days):
- Prophylaxis (10 days): same weight-based doses given once daily 5
- Infants 9-11 months: 3.5 mg/kg per dose 5
- Term infants 0-8 months: 3 mg/kg per dose 5
Critical Prescribing Practices
Essential Prescription Elements
Every pediatric prescription must include 3:
- The total daily dose (mg/kg/day)
- Number of divided doses per day
- Duration of therapy
- Indication for prescription
- Child's current weight
Common Pitfalls to Avoid
- Never use age-based dosing when weight is available – this leads to 30% dosing error rates 3, 4
- Never assume "small adult dose" is appropriate – children have unique pharmacokinetic parameters requiring individualized dosing 7, 8
- Never prescribe without documenting weight – this is the single most important parameter for safe pediatric dosing 3, 7
- For acetaminophen, avoid the 10 mg/kg dose as it is subtherapeutic; use 15 mg/kg 4
- For amoxicillin in common infections, the simplified 60 mg/kg/day in 2 divided doses is more practical and reduces prescriber-pharmacist conflicts 3
Renal Impairment Adjustments
- For amoxicillin in severe renal impairment (GFR <30 mL/min): reduce frequency to every 12-24 hours depending on severity 2
- Patients on hemodialysis require additional dosing during and after dialysis 2
- Children <12 weeks have incompletely developed renal function and require dose reduction even without diagnosed renal impairment 2